John Gill Commentary Genesis 42:2

"And he said, Behold, I have heard that there is grain in Egypt: get you down thither, and buy for us from thence; that we may live, and not die." — Genesis 42:2 (ASV)

And he said, behold, I have heard that there is corn in Egypt ,
&c.] This explains what is meant by the phrase he saw, one sense being put for another: get you down thither ;
as fast as you can without delay; Egypt lay lower than Canaan, and therefore they are bid to go down, as when they went from thence to Canaan they are said to go up, (Genesis 45:25) ; and buy for us from thence, that we may live, and not die ;
which shows the famine was very pressing, since, unless they could buy corn from Egypt they could not live, but must die.